Theatre lighting currently consists of a plurality of light fixtures that are manually set for all their parameters, such as aim (pan & tilt), beam colour, beam size, gobo pattern and shuttering (shaping) of the beam, focus of the edge of the projected light pool or gobo (hard to soft) and then left that way for the current performance (show). These parameters are set to a very high degree of accuracy to satisfy the designer's requirements. To achieve a new parameter, these light fixtures have to be manually changed or else another fixture installed with the appropriate parameters manually set and that fixture turned on as needed. The intensity of the light beam of the lights is controlled by a centralized computer dimmer console. To achieve lighting cues (looks) a designer/technician uses the combination of light fixtures set to their parameters, the intensity control of the dimmer console and the console's crossfading control between dimmers to achieve cues. The limits of this system are that much time, equipment and manual labour is involved to set the lights for each production and again to change the lights for another production. Also, there are physical space limits to the number of manual light fixtures that can be located at any position about the stage.
The history of lighting in theatre, dance and opera has concerned itself primarily with using these manual lighting fixtures. During a performance, these manual light fixtures do not dynamically move except for changes in the intensity of the light beams being projected. In U.S. Pat. No. 4,392,187 by Bornhorst, the lighting system described has a large number of remotely controlled light fixtures and a central processor in a central control console which generates commands that are sent directly to the lights for controlling each of the lighting parameters of the light fixtures. This system is essentially a real time control of moving light beams with computer assistance to help the operator to execute elaborate moving affects. Each of the light fixtures is controlled for pan, tilt, acceleration, intensity, colour and beam shape. Digital commands for each of the fixture parameters are transmitted from the central processor, which is in a console, through a relatively high speed data link to each of the light fixtures. The fixtures respond to data transmitted by the operation of control knobs or faders on the console with talk-back from the fixtures to report to the central processor when each of its parameters is positioned. This system is designed to facilitate dynamic light fixture movement, as used in the music concert industry and requires very powerful and fast CPUs in a dedicated control console and a very high speed data link to communicate back and forth to each light unit. If an interruption or noise happens in the communication the light units fail or operate with errors.
Another system is described in U.S. Pat. No. 4,980,806 to Taylor, et al., which describes a moving light system like the Bornhorst system except that the processing is distributed to a lamp processor in each multiple parameter light fixture. There is feedback from sensors for each parameter to read the parameter's location and record it into the lamp's memory. An upload command transfers all the recorded cue data from all the individual lamp memories to the disk storage on the central control console. The control console allows for manual control of the lamps as well as execution of cues stored in each lamp by means of a broadcast cue from the console. This system again is designed to facilitate dynamic light fixture movement and requires two-way communication between a dedicated console and the light unit to a) allow manual control of the light unit, and b) to record the parameter cue data to a safe storage medium in the console. It also requires precise position encoder sensors for each parameter to instruct its lamp processor what its value is to enable control from the centralized console and to record the parameter values for later recall. This creates further potential for failure and error should there be a fault. Also, this system does not allow for setting the light unit's parameters except by manual manipulation of the central consols faders or control knobs.
All multi-parameter light fixtures currently developed are designed to meet the needs of a dynamic moving light effect and not the automation of the basic manual light fixture which is almost exclusively used to meet the needs in theatre, opera and ballet. Therefore, there exists a need for a new configuration and method of operation of an automated stage lighting system which tries to truly automate the manual stage luminaire, the ellipsoidal spotlight.